Modafinil, C15H15NO2S, also known as 2-(benzhydrylsulfinyl) acetamide, or 2-[(diphenylmethyl) sulfinyl] acetamide, is a synthetic acetamide derivative with wake-promoting activity, the structure of which has been described in French Patent No. 78 05 510 and in U.S. Pat. No. 4,177,290 ('290), and which has been approved by the United States Food and Drug Administration for use in the treatment of excessive daytime sleepiness associated with narcolepsy. Modafinil has been tested for treatment of several behavioral conditions in combination with various agents including apomorphine, amphetamine, reserpine, oxotremorine, hypnotics, yohimbine, 5-hydroxytryptophan, and monoamine oxidase inhibitors, as described in the cited patents. A method of preparation of a racemic mixture is described in the '290 patent and a method of preparation of a levorotatory isomer is described in U.S. Pat. No. 4,927,855 (both incorporated herein by reference). The levorotatory isomer is reported to be useful for treatment of hypersomnia, depression, Alzheimer's disease and to have activity towards the symptoms of dementia and loss of memory, especially in the elderly.
The primary pharmacological activity of modafinil is to promote wakefulness. Modafinil promotes wakefulness in rats (Touret et al., 1995; Edgar and Seidel, 1997), cats (Lin et al., 1992), canines (Shelton et al., 1995) and non-human primates (Hemant et al, 1991) as well as in models mimicking clinical situations, such as sleep apnea (English bulldog sleep disordered breathing model) (Panckeri et al, 1996) and narcolepsy (narcoleptic canine) (Shelton et al, 1995).
Modafinil has also been described as an agent with activity in the central nervous system, and as a useful agent in the treatment of Parkinson's disease (U.S. Pat. No. 5,180,745); in the protection of cerebral tissue from ischemia (U.S. Pat. No. 5,391,576); in the treatment of urinary and fecal incontinence (U.S. Pat. No. 5,401,776); and in the treatment of sleep apneas and disorders of central origin (U.S. Pat. No. 5,612,379). U.S. Pat. No. 5,618,845 describes modafinil preparations of a defined particle size less than about 200 microns. In addition, modafinil may be used in the treatment of eating disorders, or to promote weight gain or stimulate appetite in humans or animals (U.S. Provisional Patent Application No. 60/150,071, incorporated herein by reference), or in the treatment of attention deficit hyperactivity disorder (ADHD), or fatigue, especially fatigue associated with multiple sclerosis (U.S. Provisional Patent Application No. 60/149,612, incorporated herein by reference).
Modafinil was known in the art in the form of a therapeutic package, marketed under the name Provigil®. Provigil® is a pharmaceutical product manufactured by Cephalon, Inc. of West Chester, Pa. and is also marketed by Cephalon, Inc. Provigil® is supplied as tablets containing 100 mg or 200 mg modafinil, with several excipients, including magnesium silicate and talc. In commercial use, modafinil-containing therapeutic packages in the prior art were labeled and otherwise indicated for use in narcolepsy patients.
It is desirable to optimize the formulation of a solid dose form of modafinil, and the methods of their preparation on a commercial scale. In particular, new formulations of modafinil have been discovered which exhibit comparable stability, dissolution rate, hardness, friability, thickness, disintegration, size and shape, and weight variation characteristics to that of Provigil®. Further, it has been discovered that a solid dose forms of modafinil can be prepared, with properties similar to that of Provigil®, without inclusion of magnesium silicate or talc.
In addition, the newly discovered formulations preferably use a minimal number of excipients, and use pharmaceutical grade excipients that are inexpensive, readily available and that facilitate cost-effective manufacture on a commercial scale.
Furthermore, there is a need to improve upon the manufacturing process of the tablet form of modafinil. Improvement in the commercial preparation include minimizing the number of excipients, eliminating the use of organic solvents, reducing the number of steps, and reducing the time and expense of manufacture. The present invention is directed to these, as well as other, important ends.